As is known in the art of computer systems, devices such as the processor, the memory, and input/output devices communicate by transmitting and receiving signals along a signal interface bus to which the devices are coupled. More particularly, such devices include a driver circuit which couples signals to the bus for transmission to other devices, and a receiver which couples signals from the bus to the devices. In order to reduce undesirable signal reflections, generally the signal bus is terminated, such as by a resistive network, at the ends thereof so that the impedance of the bus matches that of the driver circuits. However, since termination is achieved at the ends of the bus, it often becomes necessary to change the location of terminators along the signal bus, such as when the bus is extended. That is, when the computer system configuration is modified, often the location of the terminators must also be changed so that the terminators remain at the ends of the signal bus.
As is also known, the signals carried by a signal interface bus are logic signals characterized as being in either a logic high state or a logic low state. More particularly, a logic low state may correspond to a voltage level below a first predetermined value and a logic high state may correspond to a voltage level above a second predetermined value, and the first and second predetermined values may or may not be equal. For example, in the case of a conventional SCSI (Small Computer Systems Interface) bus receiver, a voltage level below 0.5 volts corresponds to a logic low state and a voltage level above 2.0 volts corresponds to a logic high state. Often the integrity of such logic signals is degraded in that the high and/or low logic state voltage levels thereof do not correspond to the desired voltage levels or amplitudes. Such degradation may result from a mismatch between the impedance of the bus cable and the impedance of the terminator.